Quantitation of left ventricular myocardial fiber hypertrophy and interstitial tissue in human hearts with chronically increased volume and pressure overload.

Using new techniques, we quantitated left ventricular myocardial fiber hypertrophy and interstitial tissue in four groups of autopsied hearts free of coronary disease: 1) 22 normal hearts, 2) 20 hearts from patients with mitral incompetence (NYHA Class II-III) who died early after mitral valve replacement from causes other than cardiac failure, 3) 22 hearts from patients with mitral incompetence (NYHA Class III-IV) who died early after mitral valve replacement from cardiac failure with low cardiac output syndrome, and 4) 22 hearts from patients with hypertensive heart disease (NYHA Class II-III). Myocardial fiber hypertrophy was quantitated by measuring cross-sectional myocardial fiber diameter; the proportion of interstitial tissue was quantitated by using a computerized, high-resolution video image-digitizing system. Myocardial fiber average diameter in groups 2, 3 and 4 was significantly higher than group 1. The proportion of interstitial tissue was significantly increased in group 3. In chronic mitral incompetence an increase in left ventricular interstitial tissue may play a role in the development of severe cardiac failure.